Days of dormice

WE often think of dormice as sleepy animals. Many pictures depict them curled up, oblivious to the world about them - and I'm sure there are times when some of us feel a little envious of them, when we have to carry on with our daily routines during the cold weather.

WE often think of dormice as sleepy animals. Many pictures depict them curled up, oblivious to the world about them - and I'm sure there are times when some of us feel a little envious of them, when we have to carry on with our daily routines during the cold weather.

But there are two parts to a dormouse's life - each being roughly half the year and highly contrasting in terms of activity. From April to October they are active nocturnal climbers, foraging in the canopy and rarely ever seen, although sometimes there is evidence of hazel nuts eaten by them or, occasionally, their woven nests. They can climb to the highest trees and rarely come down to the ground - they have few predators as they are usually too quick and agile amongst the twiggy branches to be picked off by an owl.

In late autumn they return to the ground to build a hibernation nest and they remain there until the following spring. This is a strategy to save energy and avoid winter food shortages, but they can also return to torpor at any time of the year if the weather conditions are unfavourable, although this can have the effect of delaying the breeding season.

Because dormice are so elusive, it's only in the last five years that conservationists have really begun to understand the habitat needs for dormice in a Suffolk context and how this can be used to predict where they might live. Without this information it would be difficult to safeguard the remaining populations or to start to develop a strategy to address the problems of isolation and fragmentation.

Dormice have always been very scarce in Suffolk. The majority of our records relate to ancient woodlands and hedgerows within the area of the River Stour on the Suffolk/Essex borders, with few others outside this area. Even historical reports from a century ago describe them as being absent from as much as half of Suffolk, with no evidence further north of Thurston, east of Bury St Edmunds.

Work is now underway to survey as much suitable habitat as possible, using specially-designed plastic nest tubes to try to see where dormice are present. These are placed at shoulder height along woodland and ride edges and within suitable hedgerows. The animals can make characteristic woven nests, within the tubes. They often use stripped honeysuckle bark with a hazel leaf covering, but we have also noted that they sometimes use grass, bracken and on one occasion holly leaves!

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This work has been part of a joint initiative, the Essex and Suffolk Dormouse Project (affiliated to both Suffolk and Essex Wildlife Trusts), set up in 2002 and funded by a three year English Nature Biodiversity Grant. Dormice are strictly protected by law, so those involved have to hold special licences to allow them to undertake this exciting work. It's easy to record dormice if they are sleepy, but if they choose to be fully active.

It pays to have nimble fingers when checking the tubes, as they are liable to shoot up your arm and back into the bushes before you can say 'mouse'!

Our surveys have focused on areas within their historical range. Former habitats were re-surveyed to establish whether dormice were still there, but we also took the opportunity to survey ancient woodlands and hedgerows where no previous records existed.

Many of the remaining populations are still vulnerable to extinction because numbers are simply too low to be viable in the long term. Dormice naturally live at low densities, even in the best habitats there are typically only between five and ten animals per hectare.

Computer modelling by national researchers indicates that a population of around 20 animals has a 50per cent chance of early extinction, so dormice living in many small woods in Suffolk are really existing on a knife edge, unless ways can be found to link them up or to create additional habitat.

This means that opportunities are sought wherever possible to plant new hedgerows or gap up existing ones close to where dormice are known to live.

This is generally most effective when we work in partnership with other organisations such as Suffolk County Council, the Dedham Vale and Stour Valley Project, the Gipping Valley Project and, of course, first and foremost with the agreement of the landowner.

There are now real and exciting opportunities to address the decline of dormice in our county and ensure that our remaining populations are secure for the long-term future.


The best habitats appear to be where there is a vigorous, un-shaded shrub layer, interspersed by a few mature trees, with a wide variety of species producing a range of food during the spring, summer and autumn.

A supply of hazel is particularly important for its nuts, but other species must fill the gap at other times of the year. Climbers such as honeysuckle and brambles will provide additional food sources and link the habitat to provide high-level routes within the canopy for this highly arboreal small mammal.

Dormice feed on nectar and pollen, fruits, nuts and seeds as they become available through the year. In addition, insects such as caterpillars and aphids form an important part of their diet, so trees such as oak, which support a high biomass of invertebrates are also important in summer when there can be a shortage of flowers and fruit. This specialised diet is necessary because unlike other small rodents, their digestive system cannot process 'roughage' in the form of leaves, so they are dependent on finding quality food through the seasons. This can be a problem for dormice, particularly in spring when food can be scarce, and this becomes even more difficult for dormice living in areas where there isn't much variety in shrub species.

Hedgerows can also provide good habitat for dormice, supporting permanent populations or providing corridors connecting woodland sites, lined with food. The size of the hedgerow is important, as on average they need to be about four metres wide to support dormice and ideally of similar height.

The diversity of shrub species in a hedge is also a critical feature, as is how regularly hedgerows are managed. Hedges that are flailed annually to cut the top and sides will not support dormice because most of their flowers and berries will be removed. All the known dormouse records for hedgerows relate to sites that are connected to ancient woodlands, usually within 500m and it is likely that this factor is fundamental to the long-term survival of these animals.

Loss of woodland during the last 100 years will have had a major impact on dormice, but abandonment of the traditional ways of coppicing woodland has also had the effect of changing the woodland structure so that the underside is shaded and less productive. Removal of hedgerows has meant further habitat losses, but also compounds the effects of isolation, and fragmentation.

They are mostly found in Europe, although some live in Africa and Asia.

They were considered a delicacy in ancient Rome, either as a savoury appetiser or as a desert dipped in honey and poppy seeds.

They are only about two to three inches long, and live for up to five years.

They eat fruit, berries, flowers, nuts and insects.

They can hibernate six months out of the year, and longer if the weather stays cool.

Their name comes from the Anglo-Norman 'dormeus' which means 'sleepy one.'

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